This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Aspergillus fumigatus is a filamentous fungus that is the most frequent causal agent of invasive mold infections in immunocompromised patients. We currently have a limited understanding of the mechanisms used by A. fumigatus to survive and cause disease in immunocompromised hosts. During mammalian pathogenesis, all pathogenic microbes are exposed to rapidly changing oxygen levels. Oxygen is the critical electron acceptor in aerobic respiration and organisms must possess alternative mechanisms to deal with low oxygen (hypoxic) conditions found at sites of infection. Our hypothesis is that A. fumigatus utilizes an alcohol fermentation pathway to survive hypoxic microenvironments found in vivo during invasive pulmonary aspergillosis. This hypothesis is founded on preliminary data from metabolomics studies of A. fumigatus infected murine bronchoalveolar lavages showing the production of ethanol in vivo during fungal infections. We are exploring whether this alcohol fermentation pathway is important for A. fumigatus to cause disease by generating genetic mutants of A. fumigatus that are deficient in their ability to respond to low oxygen conditions via the use of an alcohol fermentation pathway. In the past year, we have examined the ability of these alcohol deficient strains for fungal virulence and found that loss of alcohol fermentation does not affect the capability of A. fumigatus to cause disease. However, intriguingly, loss of ethanol production results in significant changes in the types and numbers of innate immune effector cells that are recruited to the site of infection, Moreover, ethanol fermentation mutants have reduced fungal burden in the lungs of infected mice suggesting that loss of ethanol fermentation alters the pathogenesis of invasive pulmonary aspergillosis. The results of this proposal have potential clinical significance via direct manipulation of oxygen levels at sites of fungal infection and also the potential to generate increased efficacy of current antifungal drugs.